From b633c05136544aff3e06c1a93d65e6c15f77ac1a Mon Sep 17 00:00:00 2001 From: Yury Norov Date: Sat, 19 Aug 2023 07:12:35 -0700 Subject: [PATCH] sched/topology: Fix sched_numa_find_nth_cpu() in CPU-less case [ Upstream commit 617f2c38cb5ce60226042081c09e2ee3a90d03f8 ] When the node provided by user is CPU-less, corresponding record in sched_domains_numa_masks is not set. Trying to dereference it in the following code leads to kernel crash. To avoid it, start searching from the nearest node with CPUs. Fixes: cd7f55359c90 ("sched: add sched_numa_find_nth_cpu()") Reported-by: Yicong Yang Reported-by: Guenter Roeck Signed-off-by: Yury Norov Signed-off-by: Ingo Molnar Reviewed-by: Yicong Yang Cc: Mel Gorman Link: https://lore.kernel.org/r/20230819141239.287290-4-yury.norov@gmail.com Closes: https://lore.kernel.org/lkml/CAAH8bW8C5humYnfpW3y5ypwx0E-09A3QxFE1JFzR66v+mO4XfA@mail.gmail.com/T/ Closes: https://lore.kernel.org/lkml/ZMHSNQfv39HN068m@yury-ThinkPad/T/#mf6431cb0b7f6f05193c41adeee444bc95bf2b1c4 Signed-off-by: Sasha Levin --- kernel/sched/topology.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c index 05a5bc6..423d089 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -2122,12 +2122,16 @@ static int hop_cmp(const void *a, const void *b) */ int sched_numa_find_nth_cpu(const struct cpumask *cpus, int cpu, int node) { - struct __cmp_key k = { .cpus = cpus, .node = node, .cpu = cpu }; + struct __cmp_key k = { .cpus = cpus, .cpu = cpu }; struct cpumask ***hop_masks; int hop, ret = nr_cpu_ids; rcu_read_lock(); + /* CPU-less node entries are uninitialized in sched_domains_numa_masks */ + node = numa_nearest_node(node, N_CPU); + k.node = node; + k.masks = rcu_dereference(sched_domains_numa_masks); if (!k.masks) goto unlock; -- 2.7.4